Controlled quantum teleportation and secure direct communication

We present a controlled quantum teleportation protocol. In the protocol, quantum information of an unknown state of a 2-level particle is faithfully transmitted from a sender (Alice) to a remote receiver (Bob) via an initially shared triplet of entangled particles under the control of the supervisor Charlie. The distributed entangled particles shared by Alice, Bob and Charlie function as a quantum information channel for faithful transmission. We also propose a controlled and secure direct communication scheme by means of this teleportation. After insuring the security of the quantum channel, Alice encodes the secret message directly on a sequence of particle states and transmits them to Bob supervised by Charlie using this controlled quantum teleportation. Bob can read out the encoded message directly by the measurement on his qubit. In this scheme, the controlled quantum teleportation transmits Alice's message without revealing any information to a potential eavesdropper. Because there is not a transmission of the qubit carrying the secret message between Alice and Bob in the public channel, it is completely secure for controlled and direct secret communication if perfect quantum channel is used. The feature of this scheme is that the communication between two sides depends on the agreement of the third side.Comment: 4 page

Strong energy enhancement in a laser-driven plasma-based accelerator through stochastic friction

Conventionally, friction is understood as an efficient dissipation mechanism depleting a physical system of energy as an unavoidable feature of any realistic device involving moving parts, e.g., in mechanical brakes. In this work, we demonstrate that this intuitive picture loses validity in nonlinear quantum electrodynamics, exemplified in a scenario where spatially random friction counter-intuitively results in a highly directional energy flow. This peculiar behavior is caused by radiation friction, i.e., the energy loss of an accelerated charge due to the emission of radiation. We demonstrate analytically and numerically how radiation friction can enhance the performance of a specific class of laser-driven particle accelerators. We find the unexpected directional energy boost to be due to the particles' energy being reduced through friction whence the driving laser can accelerate them more efficiently. In a quantitative case we find the energy of the laser-accelerated particles to be enhanced by orders of magnitude.Comment: 14 pages, 3 figure

Direct laser acceleration of electrons assisted by strong laser-driven azimuthal plasma magnetic fields.

A high-intensity laser beam propagating through a dense plasma drives a strong current that robustly sustains a strong quasistatic azimuthal magnetic field. The laser field efficiently accelerates electrons in such a field that confines the transverse motion and deflects the electrons in the forward direction. Its advantage is a threshold rather than resonant behavior, accelerating electrons to high energies for sufficiently strong laser-driven currents. We study the electron dynamics via a test-electron model, specifically deriving the corresponding critical current density. We confirm the model's predictions by numerical simulations, indicating energy gains two orders of magnitude higher than achievable without the magnetic field

Detailed Modeling and Experimental Assessments of Automotive Dry Clutch Engagement

© 2013 IEEE. The characteristics of the clutch engagement process would have significant influences on the torque transmissibility and operation comfort. However, some crucial components are simplified in many previous literature, which would cause imprecision. Therefore, it is important to build a detailed mathematical model of these components and inspect the whole process of clutch engagement. In order to improve the torque transmissibility and achieve better pedal releasing comfort, solutions based on the modeling of the clutch cover assembly and the friction disc assembly, the analysis of the clamping force and the releasing characteristics of the release bearing are proposed in this paper. Furthermore, models of the crucial components such as the diaphragm spring, which connects the straps and cushion plate, are built and the corresponding mechanical properties are analyzed. Based on the manufacturing tolerance, the life cycle, and the wear properties, diaphragm spring correction formula is proposed by referring to Almen-Laszlo method. On the system level, the whole engagement process is divided into four stages because of the differences between the engaging and disengaging processes, which would affect the pedal releasing comfort in the manual transmission system and the shifting quality in the automated transmission system. To demonstrate the effectiveness of the proposed method, detailed mathematic models are built and the corresponding experiments are conducted